Generally, a vehicle is provided therein with seat belts, which restrain passengers as well as a driver for the sake of safety in crash, in order to attenuate deceleration exerted on a body of the passenger. The seat belt retrains the passenger in the event of a collision.
In addition to the seat belt, the vehicle is provided with an airbag module rapidly inflating an airbag between a driver and a steering wheel or between a passenger in a passenger seat and an instrument panel in crash to attenuate the injury of the driver or the passenger caused by impact occurring in the crash.
FIG. 1 is a perspective view schematically showing an airbag module according to the related art. As shown in FIG. 1, a passenger airbag module 100 for a vehicle includes an inflator 110, an airbag cushion 120, and a tether 130. The inflator 110 generates nitrogen gas (N2) upon explosion of a detonator. The airbag cushion 120 expands and deploys through a deployment part by nitrogen gas generated from the inflator 110. The tether 130 connects a front part of the airbag cushion 120, which makes contact with the body of the passenger, with a rear part of the airbag cushion 120, into which the N2 is injected from the inflator 110.
The airbag module further includes an impact sensor (not shown) and an electronic control module (not shown). The impact sensor is installed in the instrument panel to generate an impact signal when a driving speed of the vehicle is abruptly decreased or the acceleration of gravity reaches a setting value. The electronic control module explodes the detonator of the inflator 110 according to the impact signal.
The inflator 110 of the airbag module 100 includes a gas generating agent generating the N2 as the detonator of the inflator 110 is ignited, and the tether 130 is deployed by the nitrogen gas in a state in which the tether 130 is wound around the inflator 110.
In order to constantly maintain the deployment length of the airbag cushion 120, the tether 130 includes a first support part 131a fixing one end of the tether 130 to the rear part of the airbag cushion 120 and a second support part 131b fixing the other end of the tether 130 to the front part of the airbag cushion 120.
Regarding the operation of the airbag module 100 having the above structure, when the driving speed of the vehicle is abruptly decreased due to head-on crash, the impact sensor detects the impact occurring in the head-on crash and generates the impact signal.
At this time, the electronic control module recognizes the impact signal, so the electronic control module ignites the detonator of the inflator 110 to burn the gas generating agent of the inflator 110, so that the gas generating agent rapidly generates the nitrogen gas. While moving from gas exhaust ports 111 formed in the inflator 110 to a gas injection port 121 of the airbag cushion 120, the nitrogen gas expands and deploys the airbag cushion 120 toward the passenger.
The deployed airbag cushion 120 makes contact with the passenger to partially absorb impact. In addition, when the deployed airbag cushion 120 collides with the head or the breast of the passenger by inertia, the N2 of the airbag cushion 120 is rapidly exhausted through gas exhaust holes of the airbag cushion 120 to attenuate the impact exerted on the front part of the passenger.
Accordingly, impact power applied to the passenger in the crash of the vehicle is effectively attenuated, so that the second collision, that is, the collision between other components of the vehicle and the body of the passenger can be reduced.
However, when the tether 130 wound around the inflator is deployed by the N2, the tether 130 cannot be linearly deployed toward the passenger, but can be spirally deployed due to the increase of the friction between the inflator and the tether. In addition, when the tether 130 is spirally deployed, the tether 130 may be twisted so that the deployment length of the airbag cushion is reduced, and the impact absorbing effect is reduced at the front of the passenger due to the reduction in deployment length of the airbag cushion. Accordingly, the airbag cushion may be abnormally deployed.